This disclosure is directed to thermoplastic compositions, articles formed therefrom, and their methods of manufacture, and in particular thermoplastic compositions with advantageous properties such as improved impact strength and chemical resistance.
Polycarbonates are useful in a wide variety of applications at least in part because of their good balance of properties, such as moldability, heat resistance and impact properties, among others. However, the performance of polycarbonates themselves may not be sufficient to meet application requirements on chemical resistance for certain applications. For example, in order to be used in mobile phones, materials have to pass environmental stress-cracking resistance (ESCR) testing at 0.5 or 1% strain after exposing to a sunscreen. Another important requirement is low temperature impact having ductility at temperatures of −10° C., −30° C. or lower, depending on the application and design.
Blending of polycarbonates with other polymers with good chemical resistance may improve the ESCR resistance of the polycarbonates, but the addition of the polymers such as poly(ethylene terephthalate) or polyetherimide results in poor impact performance. Since low temperature impact (ductility) is another key requirement, such materials would not be suitable for mobile phone applications.
Despite extensive research on these materials over the years, there still remains a need in the art for improved thermoplastic compositions that have balanced chemical resistance and low temperature impact properties.